1. Field of the Invention
The present invention generally relates to a transmission device, and more particularly to a transmission device of automatic document feeder.
2. The Related Art
With the development of softwares and hardwares, a scanner has become one of basic equipments of a computer user. Words and images of documents, magazines, books, pictures and so on, can be scanned into a computer and processed by the scanner. Generally, the scanner includes a motor, a transmission mechanism and a scanning unit. The transmission mechanism includes a gear assembly disposed on the scanning unit, and a transmission belt. When the documents are to be scanned, two scanning ways are capable of being applied. One of the scanning ways is described as follows: the motor drives the transmission mechanism to bring along the scanning unit to scan the documents located above the scanning unit. In order to improve an efficiency of scanning the documents, the scanner further includes an automatic document feeder. The other scanning way is described as follows: the scanning unit is without being moved, the transmission mechanism drives the documents to be scanned by the scanner with the automatic document feeder to achieve an image scanning purpose as well.
Referring to FIG. 1, a conventional automatic document feeder 100′ has a passageway for transmitting papers. The passageway includes an input tray 10′, a paper-feed channel 11′, a scanning channel 12′, a paper-out channel 13′ and an output tray 14′. In order to make the papers transmitted through the passageway, the conventional automatic document feeder 100′ further includes a scanning unit located under the scanning channel 12′, and a transmission device disposed along the passageway. The transmission device generally includes a pickup device 15′ and a plurality of feeding rollers 16′. The pickup device 15′ is disposed to an entrance of the paper-feed channel 11′. The feeding rollers 16′ are disposed along the paper-feed channel 11′ and the paper-out channel 13′.
When the papers are scanned, the pickup device 15′ will press downward on the papers which are placed in the input tray 10′ to start feeding a top piece of the papers into the paper-feed channel 11′, the feeding rollers 16′ rotate towards a single direction to feed the paper into the scanning channel 12′, the scanning unit reads images of the paper, and the scanned paper is transmitted into the output tray 14′. When the scanning of the paper is to be cancelled midway by a user, a cancelling button is pressed, the conventional automatic document feeder 100′ stops working. Then a cover of the scanner is opened, and the paper is pulled out.
However, the paper is easily damaged in the process of the paper being pulled out, the conventional automatic document feeder 100′ mostly needs at least two motors, clutches or magnetic valves and so on to drive the pickup device 15′ and the feeding rollers 16′ that increases a volume of the conventional automatic document feeder 100′ and a manufacturing cost of the conventional automatic document feeder 100′.
In order to solve the above-mentioned problems, an innovative transmission device of automatic document feeder and an innovative automatic document feeder are essential to be provided to decrease a volume of the innovative automatic document feeder and a manufacturing cost of the innovative automatic document feeder.